Epidemiology and Infection

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Epidemiology and Infection (2009), 137:913-921 Cambridge University Press
Copyright © Cambridge University Press 2009

Review Article

Giardia and Cryptosporidium infections in sheep and goats: a review of the potential for transmission to humans via environmental contamination


a1 Parasitology Laboratory, Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, Oslo, Norway
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robertson lj [PubMed]  [Google Scholar]


The public health significance of giardiasis and cryptosporidiosis in sheep is currently unclear. Some research suggests that they are probably not an important zoonotic reservoir, whilst other research indicates this potential exists, and some outbreaks have also been associated with infections in sheep. Actions to limit water supply contamination by sheep have sometimes been severe, occasionally creating problems between farming and public health communities. Here our knowledge on these parasites in both sheep and goats is reviewed; although direct evidence of transmission to humans via water supply contamination is limited, the data accrued indicate that this is a real possibility. As cryptosporidiosis in sheep is generally more prevalent than giardiasis, and species/genotypes of Cryptosporidium infections in sheep are likely to be infectious to humans, this parasite may be considered the greater threat. Nevertheless, geographical variation in prevalence and genotypic distribution is extensive and as measures to limit sheep grazing can have a highly negative impact, it is important that cases are judged individually. If water contamination from a particular population of sheep/goats is suspected, then suitable investigations should be instigated, investigating both prevalence and species/genotype, before precautionary measures are imposed.

(Accepted January 27 2009)

(Online publication March 10 2009)

Key Words:Cryptosporidium; Giardia; goats; sheep; waterborne transmission


c1 Author for correspondence: Dr L. J. Robertson, Parasitology Laboratory, Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, PO Box 8146 Dep., 0033 Oslo, Norway. (Email: Lucy.robertson@veths.no)